KVM: add basic paravirt support

Add basic KVM paravirt support. Avoid vm-exits on IO delays.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>

3 files changed, 4 insertions, 1 deletions

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 621a8e362fe7..1b9e695cc641 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -820,6 +820,7 @@ int kvm_dev_ioctl_check_extension(long ext)
         case KVM_CAP_EXT_CPUID:
         case KVM_CAP_CLOCKSOURCE:
         case KVM_CAP_PIT:
+        case KVM_CAP_NOP_IO_DELAY:
                 r = 1;
                 break;
         case KVM_CAP_VAPIC:
diff --git a/include/asm-x86/kvm_para.h b/include/asm-x86/kvm_para.h
index 5ab7d3dbd357..ed5df3a54aab 100644
--- a/include/asm-x86/kvm_para.h
+++ b/include/asm-x86/kvm_para.h
@@ -10,7 +10,8 @@
  * paravirtualization, the appropriate feature bit should be checked.
  */
 #define KVM_CPUID_FEATURES      0x40000001
-#define KVM_FEATURE_CLOCKSOURCE 0
+#define KVM_FEATURE_CLOCKSOURCE         0
+#define KVM_FEATURE_NOP_IO_DELAY        1
 
 #define MSR_KVM_WALL_CLOCK  0x11
 #define MSR_KVM_SYSTEM_TIME 0x12
diff --git a/include/linux/kvm.h b/include/linux/kvm.h
index a2f3274016ee..76f09474be98 100644
--- a/include/linux/kvm.h
+++ b/include/linux/kvm.h
@@ -237,6 +237,7 @@ struct kvm_vapic_addr {
 #define KVM_CAP_NR_VCPUS 9       /* returns max vcpus per vm */
 #define KVM_CAP_NR_MEMSLOTS 10   /* returns max memory slots per vm */
 #define KVM_CAP_PIT 11
+#define KVM_CAP_NOP_IO_DELAY 12
 
 /*
  * ioctls for VM fds